The purpose of the present research is to increase our understanding of the basic processes of learning and memory, and, in particular, to analyse the changes in those processes that occur during the normal course of development. The specific goals are to study the development of (1) habituation and sensitization, (2) sensory information processing, (3) short-term memory, (4) long-term memory, and (5) stimulus generalization in the preweanling rat. Related studies will analyse the effects of motivation and interpolated experience on learning and memory during development. Of particular interest will be the interrelationship between these different forms of learning. Do they develop sequentially from the simplest to the most complex, from habituation to long-term memory? Or do they develop simultaneously?